The invention relates generally to an arrangement which is variously known as a burner or jet, or blowing nozzle, for example for use in a metallurgical furnace, for injecting for example a fuel such as a fuel gas and one or more other gases, into the interior of the furnace. For the sake of simplicity of terminology in this specification, the term nozzle or nozzle assembly will be used to denote a burner or blowing nozzle.
German published specification (DE-AS) No 20 13 145 discloses a nozzle assembly for use in a metallurgical furnace such as an arc furnace, which in use is disposed above the level of the molten bath in the furnace. In the region of the tip of the nozzle assembly, that is to say, in the region of the discharge opening thereof, that arrangement has a change-over slide member which is displaceable by pneumatic or hydraulic means, for controlling the feed of fuel gas and one or more other gases to the discharge opening of the nozzle assembly.
When using nozzle assemblies which are sometimes referred to as jet burners for oil and oxygen or fuel gas and oxygen, in a metallurgical furnace, more specifically an electric arc furnace, the mouth opening of the nozzle assembly must be kept free of metal and slag which may be deposited in that area of the nozzle assembly as by splashing. The danger of the discharge opening of the nozzle assembly becoming fouled by slag or the like is very serious in particular during the periods of time when the nozzle assembly is not operating. Similar problems also occur in regard to nozzle assemblies forming blast nozzles for injecting oxygen or an oxygen-bearing gas into a furnace.
In order to avoid fouling and corrosion due to the deposit of slag on the burner arrangement, the burner arrangement must be drawn or pivoted out of its position in the wall of the furnace during the periods of time that the assembly is not operative, by using mechanical means. Such withdrawal means are expensive and also susceptible to breakdown or failure. They also require a large amount of maintenance. Furthermore, before the burner arrangement is refitted into position in the opening in the wall of the furnace, that opening must be properly checked and if necessary any slag deposited in that area must be removed.
Another method of keeping the mouth of the burner arrangement free involves blowing air through the burner during the periods when the burner is not in operation. The effectiveness of that mode of procedure is doubtful particularly when the burner is disposed in the wall of the furnace at a very low position, when slag reaches the openings. In addition, the costs involved in producing the flow of compressed air are high.